Such rotation dobbies are known. In particular, U.S. Pat. Nos. 3,724,511 and 3,730,231 each disclose such a dobby. Both designs have a key-shafting gate as a control member, wherein the main shaft of the dobby extends through an opening in the gate and the gate for transmitting control impulses to the key carries out a swivelling movement about a fixed axis. The opening in the gear-shifting gate has a collar which projects axially with respect to the main shaft and serves as an endless cam which is constantly in engagement with a groove in the key.
Due to the small thickness of the key-shifting gate, which is possible due to the heddle frame thickness, the key-shifting gate is exposed to relatively strong bending and torsion forces. Since the shaft for the swingable support and the connecting point to the needle mechanism lie, due to the narrow heddle frame thickness, relatively far outside the range of movement of the connecting rod, the switching arm must be built very strong in order to prevent warping, bends and spring action, which requires a heavy construction and results in a certain movement inertia or, through unexpected lateral friction, misfunctions of the machine.
A first purpose of the invention is an increase in the machine speed by providing a change in the support and control of the switching arm.
Reading systems have become known, for example through U.S. Pat. No. 4,154,268, in which the patternlike control is transmitted through a power amplifier to a shed-forming mechanism of the Hattersley system, whereby the main characteristics include the power amplifier moving the reading needle toward the pattern card and thus starting the reading operation and also moving in a power-amplifying manner the control mechanism for the heddle-frame operating members, the power-amplifying movement being in the same direction as the movement of the reading needle.
In the embodiment according to U.S. Pat. No. 4,371,006, the power amplifier acts only when a different reading value is read by the reading needle from the pattern card. The return of the control parts is done by the power amplifier. In the embodiment according to U.S. Pat. No. 4,385,646, the power amplifier acts only when the reading needle encounters a perforation in the pattern card. A return spring is provided for returning the control parts. Both designs have the characteristic that, during reading of a hole of the pattern card by the reading needle, the heddle frame is moved into the upper-shed position or remains unmoved. Both designs were illustrated and described in connection with the control of the draw hooks of a dobby of the Hattersley system. However, it is also possible to use these systems for controlling the locking keys of a dobby with a rotation drive. The purpose remains the same. It is necessary only to provide a suitable connection to the controlled member, such as a draw hook, control key, etc.
A purpose of the invention is thus to provide a needle mechanism for a rotation machine such that the transfer of the reading value is transmitted in a power-amplified manner in a direction which is opposite to the direction of movement of the reading needle, wherein reversing levers for the control movement, as is for example the case in Swiss Patent No. 621 157, are not required.